Applications of quantum sources, especially the heralded single photon source in the quantum key distribution (QKD) are introduced, and a new scheme of the measurement-device-independent quantum key distribution (MDI-QKD) based on heralded single photon source is presented. Comparing with existing schemes, such as the scheme of using weak coherent sources, the new scheme has many advantages like a better security, a higher key generation rate and a longer safe transmission distance. Therefore, it seems to be a promising candidate for the implementation for the quantum key distribution in the near future.